In the construction industry where on-grade concrete floors, slabs, parking areas, and/or driveways, for example, are to be poured, the subgrade materials should be properly prepared prior to pouring the concrete. Subgrade materials may vary considerably but typically are comprised of earth, dirt, sand, gravel, stone, dust, or combinations thereof. It is highly desirable to maintain the proper design thickness of the concrete over the entire area of the pour. Generally, the subgrade materials should be leveled and smoothed prior to the concrete being placed thereon. Undesired settling or cracking of the resulting concrete slab can be limited or substantially avoided through accurate placement and compaction of the subgrade materials.
A vertical cross-section of a concrete slab that is dimensionally too thick relative to the desired slab thickness specification can be typically identified as a waste of concrete material. Excess thickness areas in the concrete slab also add to construction costs where the actual volume of the concrete required to complete the job exceeds the mathematically estimated amounts. When this happens, the expected surface coverage in square feet or meters for a pre-estimated volume of concrete may fall short of design expectations. On the other hand, a concrete slab that is dimensionally too thin in vertical cross section in a given location reduces the total strength of the concrete in that area. Concrete that is too thin or otherwise variable in thickness as a result of improper subgrade preparation and quality may also readily promote uncontrolled cracking and eventual premature failure of the slab within its expected service life.
Accurate placement and compaction of the sub-grade materials is generally known to be a challenge even with the aid of skilled personnel using generally known measuring tools and equipment. The preparation of the concrete subgrade surface is typically a manual-labor intensive undertaking. Even when operator-controlled power equipment may be utilized to help level and smooth subgrade materials, variations in the elevation of the subgrade with respect to the finished surface of the concrete may be significant. Further efforts toward perfecting the subgrade materials quickly adds to the overall cost and time invested in preparing the subgrade. Such further expenditures of resources typically do not result in a proportional improvement in the final quality of the prepared subgrade.
Therefore, there is a need in the art for an apparatus and method for providing an accurate and substantially smooth subgrade surface for the support of a concrete slab, and more specifically, to promote an improvement toward consistent vertical cross-sectional thickness in finished concrete slabs and the like.